Availability of cell lines has been central to the study of developmental, cellular and molecular biology. Several investigators have attempted to place odontogenic cells (ameloblast, odontoblast, cementoblast) in culture with several degrees of success, and although some have attempted to produced immortalized cell lines derived from pulpal cells (Sato and Ozawa, 1975; Kasugai et al. 1988) and enamel organ epithelial cells (Chen et al, 1992), none of these cells lines have been demonstrated to be capable of producing a mineralized matrix. A transgenic mice harboring the SC40 strain tsA58 early region coding sequences under the control of the mouse major histocompatibility complex H-2Kb class I promoter is now available from Charles River. This promoter is active at various levels in different tissues of the body but in the presence of interferon (IFNs) can be induced to higher levels in almost all cells. These transgenic mice (H-2Kb-tsA58) have the potential of producing cell lines derived from any different tissues, which can behave like immortal cell while in the presence of gamma-IFN at permissive temperatures and then allowed to differentiate by removing the inducer and maintained at non-permissive temperatures (Jan et al. 1991). Cell lines derived from skin fibroblasts (Jat el al, 1991), osteoclast cells (Chambers et al, 1993), colon and small intestine epithelial cells (Whitehead et al, 1993) and astrocyte cells (Groves et al, 1993) using H-2Kb-tsA58 transgenic mice have been described. In this study, we propose to test the hypotheses that dental papillae mesenchyme and enamel organ epithelial cells obtained from H-2Kb-tsA58 transgenic mice (ImmortoMouse) will behave as immortalized cells while maintained in culture in the presence of interferon and they can be induced to differentiate into odontoblast and ameloblast cells with the subsequent formation of a mineralized dentime and enamel extracellular matrix respectively by changing the culture conditions. If our hypothesis is correct, this study will represent a major breakthrough in the dental field. These cells can then be grown in high quantities and used for multiple studies such as determination of putative regulatory regions for tissues specific genes; to isolate and characterize transcription factors; to isolate and characterize other extracellular matrix components and to determine their role in biomineralization and to determine the role of growth factors, hormones, etc, thus providing a system to elucidate the mechanism that govern the molecular programs involved in tooth development. In addition, these cells lines can be used to test cements, ceramics, etc. for toxicity and biocompatibility. Furthermore, similar cell lines can be obtained for other craniofacial tissues such as cementoblast, salivary glands, periodontal ligament, palate, gingiva and osteoblast thus reducing considerably the number of animals used for these type of studies.